Piston of an internal combustion engine

ABSTRACT

The piston of an internal combustion engine is cooled by passing a coolant liquid toward the bottom of the piston along the skirt of the piston in an annular path, and thence radially inwardly in a layer along the bottom of the piston and finally axially out of the piston away from the bottom of the piston.

United States Patent Inventor Willem Marinus Burck Zierikzee, Netherlands Appl. No. 874,203 Filed Nov. 5, 1969 Patented Jan. 11, 1972 Assignee N. V. Industrieele Handelscombinatie Holland Rotterdam, Netherlands Priority Nov. 5, 1968 Netherlands 68.15749 PISTON OF AN INTERNAL COMBUSTION ENGINE 1 Claim, 1 Drawing Fig.

u.s.c1 92/186,

123/41.35,123/41.37 1m.c1 FOIp3/10 FieldolSearch 92/186;

[56] References Cited UNITED STATES PATENTS 1,157,347 10/1915 Ver Planck 92/186 X 1,547,687 7/1925 Rohwer 92/186 X 1,761,864 6/1930 Becker 123/4136 FOREIGN PATENTS 528,003 4/1954 Belgium 92/186 391,944 3/1924 Germany... 123/41.35 563,521 8/1944 Great Britain.... 123/4137 780,529 8/1957 Great Britain 123/4l.37

Primary Examiner-Martin P. Schwadron Assistant Examiner-Irwin C. Cohen Attorney-Young & Thompson ABSTRACT: The piston of an internal combustion engine is cooled by passing a coolant liquid toward the bottom of the piston along the skirt of the piston in an annular path, and thence radially inwardly in a layer along the bottom of the piston and finally axially out of the piston away from the bottom of the piston.

PATENTEB JAN] 1 I972 INVENTOR ATTORNEYS PISTON OF AN INTERNAL COMBUSTION ENGINE The invention relates to a piston of an internal combustion engine, said piston having been provided with a hollow void underneath the piston bottom, said hollow void having been provided with a coolant feed and an outlet which has been positioned and dimensioned in such a way that there is always a quantity of coolant in the hollow void, said coolant only partially filling said void. Such a piston is generally known. Cooling the piston is effected by splashing the quantity of coolant in the hollow void against the lower part of the piston bottom every time the piston moves upwards and downwards. The coolant may be supplied from the usual pressure-feed circuit of the internal combustion engine via passages in the connect ing rod and piston rod, if the latter is present. The disad- A vantage of this way of cooling the piston is that the coolant hits the surface of the piston bottom generally in a perpendicular direction, because of which in principle the coolant will not flow along the piston bottom, and the heat to be carried off will only with difficulty be transmitted to the coolant. This makes for a poor cooling of the piston bottom, causing the coolant coming in direct contact with the bottom to become overheated, because it is not regularly renewed. This may present difficulties when this oil is coming from the lubricant circuit, for example. There are constructions in which the bottom is arched. In this case there is a local flowing movement of the coolant along the bottom when it is hitting against it. There are always some regions, however, where no flowing movement will occur along the recessed parts. Those regions are at the site of those parts of the bottom surface which are entirely or substantially covered by, or abutting, a surface that is perpendicular to the central axis of the piston. This will only solve part of the problem.

It is the object of the present invention to furnish a piston with which the cooling of even those regions is considerably improved, and with which a rapid renewal of the quantity of coolant at that site and in the hollow void has become possible.

This object has been achieved according to the invention by the fact that the coolant feed empties into the hollow void via one or more orifices or slots limited in upward direction by the inner surface of the piston bottom, the orifice or slot-abutting walls having been shaped in such a way, and the orifice or slot having such dimensions with respect to the feed, that it is possible for the coolant to flow along said inner surface of the bottom in the form of a layer. Thus it has been achieved that owing to the pressure of the liquid column in the supply pipe in the uppermost reach of the upward stroke an extraordinarily powerful jet of coolant will flow along the bottom surface to be cooled, while the quantity of coolant simultaneously pressing against said bottom surface, and present in the hollow void, will be forced away from that bottom surface and admixed with the forrner flow. The excess coolant is carried out of the hollow void by way of the large and open passage of the outlet. It goes without saying that the in-flowing coolant has to overcome the back pressure of the fluid accumulated in the uppermost reach of the upward stroke against the bottom part of the piston bottom. This pressure is negligible, however, compared with the pressure occurring in the liquid column of the supply pipe as a result of the massive forces in the uppermost reach of the upward stroke and the pressure already present. Where a piston is concerned, the piston bottom of which has surface parts entirely or substantially covered by or abutting a surface perpendicular to the central axis of the piston, the orifice(s) or slot(s) are according to the invention preferably situated in the neighborhood of those surface parts. At the site of those surface parts the coolant will be inclined to flow away from the surface. By directing the jet of coolant towards those parts on purpose, it is ensured that the cooling of those parts is done properly, and the layer of coolant is constantly changed.

According to the invention the supply pipe preferably empties in the hollow void via an angular recess at the innermost side of the piston skirt. This makes for an even distribution of the coolant at the site of the slot, and cooling of the piston skirt as well.

According to the invention for a constructive realization use may be made of an insert to be constructed inside the piston, said insert having been provided with an axial bore passing through a central thickened part, said bore communicating with a discharge bore in the piston rod, said insert having an additional void situated in a concentric position around the axial bore and communicating with the supply pipe in the piston rod, and a cylindrical wall or rib which forms the annular recess together with the inner wall of the piston, in which rib the hollow void of the piston is situated and which has been provided with passages connecting the aforesaid'concentric void with the annular hollow void.

The invention will now be more fully explained with reference to the drawing wherein an embodiment of the invention is diagrammatically illustrated.

The drawing shows a piston l with a bottom 2, a skirt 3, a lower cover 4 with a piston rod 5. The piston rod is located in a crosshead 6 connected to the connecting rod 7, said connecting rod 7 being mounted on a pivot 8. Crosshead, connecting rod and pivot have not been shown in detail, as they are irrelevant to a proper understanding of the invention. In the piston 1 between the bottom 2, the cover 4, and the skirt 3 there is an insert 9 provided with a centrally thickened portion 10 with a bore communicating with the discharge bore 11 in the piston rod. In the piston rod a passage 12 has been constructed disposed concentrically around this discharge bore 11, and opening into a hollow void 13 formed between the lower part of the insert 9 and the cover 4. The insert has an annular wall or rib 14 which forms an annular hollow void 15 together with the skirt 3, ending immediately underneath the bottom 2 in such a way that an annular slot 16 is formed at the site. The insert has passages 17 which connect the annular recess 15 to the void 13.

In the piston a hollow void 18 is thus formed, in which hollow a quantity of oil is collected below and around the outlet of the discharge 11 starting in the thickened portion 10 during each lower reach of the stroke.

During the reciprocating movement of the piston the fluid column being present in connecting rod 7 and piston rod 5 in the uppermost reach of the upward stroke, said fluid column receiving its supply from the lubrication system via the pivot, will produce an extraordinarily forceful liquid flow via the void 13, the passages 17, the annular void 15, to the void 18 via the slot 16. Due to the curve in the transitional portion between the inside of the skirt and inner surface of the piston bottom, and by a right choice of the dimensions of the slot, through the slot a liquid flow will appear in the form of a layer, said flow passing along the lower part of the bottom 2 on its way inwards and taking up heat on its way, said flow mixing with the quantity of oil which is whirled upwards from the lower part. The excess oil will flow off to the sump via the discharge pipe 11. There will not be a column in the discharge pipe, which column might have an adverse action, because the open passage of the outlet is large compared with the quantity of oil to be carried off. The slot through which the stream of oil appears and will flow along the piston bottom naturally need not be at exactly the highest level of the interior bottom surface of the piston, as it is in the drawing. Neither has the slot to be of annular design. The oil may also be supplied via a number of pipes, the outlets of which end so closely below the bottom surface that a slot is obtained at the site of each pipe. lt will be obvious that another coolant may also be used instead of oil, said coolant in that case being'supplied in a different way, for instance via a separate cooling circuit.

lclaim:

l. A piston for an internal combustion engine, said piston having a piston rod connected thereto, a wall on the same side of said piston as the piston rod, a bottom on the side of said piston opposite said wall, a skirt extending between said wall and said bottom, said skirt, wall and bottom together defining a void within said piston that is partly filled with a quantity of jacent surface of said bottom a restricted passage between opposite sides of the sleeve, said surface of said bottom at the location of said restricted passage having a cross-sectional contour in the shape of a gently curved line connecting the inner surface of the skirt with a convex central portion of said bottom, said convex portion extending substantially within the cylindrical wall of said sleeve, the tangent to said curved line at a location along said restricted passage being perpendicular to the axis of the piston 1'' I! l 1 I 

1. A piston for an internal combustion engine, said piston having a piston rod connected thereto, a wall on the same side of said piston as the piston rod, a bottom on the side of said piston opposite said wall, a skirt extending between said wall and said bottom, said skirt, wall and bottom together defining a void within said piston that is partly filled with a quantity of liquid coolant, an inlet conduit and a discharge conduit for the coolant extending through said piston rod, a cup-shaped sleeve including a cylindrical wall coaxial with the piston and disposed within said void and spaced inwardly from said skirt, said cylindrical wall being closely adjacent said skirt and parallel thereto, said inlet conduit communicating with the space between said sleeve and said skirt, said outlet conduit communicating with the space within said sleeve, said sleeve terminating in a free edge disposed in line with the cylindrical contour of said sleeve, said free edge forming with the adjacent surface of said bottom a restricted passage between opposite sides of the sleeve, said surface of said bottom at the location of said restricted passage having a cross-sectional contour in the shape of a gently curved line connecting the inner surface of the skirt with a convex central portion of said bottom, said convex portion extending substantially within the cylindrical wall of said sleeve, the tangent to said curved line at a location along said restricted passage being perpendicular to the axis of the piston. 